System of control



L. 1. HIBBABD. SYSTEM OF CONTROL.

APPLICATION FILED MAY 14, 1920.

1,416,026. P tnfed May 16, 1922..

UNITED STATES PATENT OFFICE.

LLOYD .r. mmmnnor wirxrnsnone, PENNSYLVANIA, assionon r0 wnsrmenorrsn ELECTRIC & MANUFACTURING COMPANY, A CORPORATION or iE'NN- SYLV'ANIA.

s'Ys'rnia: or conrnon s ecifier-. 511 of Letters Patent. P t t d May 16, 1922 Applicatihn filed'May 14, 1920. Serial No. 381,279;

Tod wh m it may concern:-

Be it known that I, LLoim J. HIBBARD, a

citizen of the United States, and a resident of WVilkinsburg, in the county of Allegheny and State otPennsylvania, have invented a new and useful Improvement in Systems of Control, ofwlnch'the following 1s a speclfi 'One object of my invention is to provide a system of the above-indicated character, wherein'a plural-section 'resistor is associ ated With the p0ly-phase-rotor Winding of an induction motor, and Sections of the resistor are progressively excluded from cir cuit in a certain-rotation to efi'ect a smooth and uniform acceleration of the motor.

More specifically stated, it is the object of myinvention to provide a star-connected resistor device that is associated with the three-phase rotor winding of an induction motor, together with a plurality of switching devices for gradually cutting out resistance from each phase while maintaining a substantial balance of currents between the several phases.

' My invention may b'est be' understood by reference to the accompanying drawing, wherein- Figure 1 is a diagrammatic view of the tion motor 14, which iturther comprises a wound rotor-15.

A plurality of brushes 16, 17 and18 bear upon the respective collector rings of the rotor 15 and are connected through conductorsf19, 20 and 21, respectively, to a pl'u'- rality' oi star-related resistors 22, 23 and 24 which may thus be considered as respectively connected in phase A, phase B and phase 0, as indicated bythe' corresponding legends.

A plurality of preferably electricallyoperated or solenoid-type switches 1 to 6, inclusive, are associated in pairs with the re spe'ctive resistor sections; and a plurality of cam-operated switches Alto A8, inclusive, B1 to B8, inclusive, and C1 to C8, in-

clusive, are furtheradapted to be connected to various tappoints of the respective re sistors. Considering the resistor 22, for example, line switch 1 has one terminal directly connected to the outer terminal of the resistor, while the other switch terminal is connected to one stationary terminal of each of the alternately-located switches A1, A3,A5 and A7. Thesolenoid or line switch 4 has one terminal connected to the outer end of theresistor 22, while the other terminal is connected to'on e terminal or each of the remaining cam operated switches A2, A 1,-A6 and A8. The remaining'sets of both types of switches are associated with the cor-- responding resistors in a similar manner.

It will be understood that the particular type of switches that I employ is immaterial to the presentinvention, although the cited combination of electrically actuated and cam-operated switches makes for a convenien't and inexpensive arrangement. Since both the structures and the method ofeiiect in m iar to those skilled in the art, I have not deemedit necessary to further illustrate the switches or to show any auxiliary governing system for closing them inthe order specified by the sequence chart, Fig; 2.

Assuming that it is desired to etiect acceleration of the induction motor 14 the proper switches are closed to connect the primary winding 18 across the supply-circuit conductors 10, 11 and'12 and to connect the slip-rings16, 17 and'lS to the outer ends of-the resistors 22, 23 and 24,'rjespectively,

as illustrated, all of the switches that are directly associated with the resistors being initially open.

To increase. the motor speed, the controlling device, of whatever character selected, is actuated one step forward to its position a, whereby the line switch 1 and'the camswitches A1 and B1 are closed, as indicated by the corresponding line in the sequence chart; The simultaneous closure of switches .l and A1 short-circuits the outermost secg'closure of the various switches are ta 1 iii) rent traversing phase A of the inductionmotor-secmidary winding As soon as the controller is moved to po sition o, line switch 2 and cam switch C1 are closed. Since the switches 2 and 131 are now both closed, the outermost section or block the resistor 23 is likewise shortcircuited.

in position 0, line switch 3 and cam switch A2 are closed. In this way, the outermost section of the resistor 2% is short-circuited.

In other words, the first three steps of the controller serve to progressively exclude equal sections of resistance from the circuits of all three-phase windings In position (Z, line switch 4% closes. and, since the cam switch as was closed in position c, an additional block of the resistor 22 is thus short-circuited. The switch B2 is also closed in this position, and, as soon as the controller reaches position 6, the closure of switch 5, conjointly with the s viitch E2, serves to short-circuit another section of the resistor 23.

Cam switch C2 is also closed in position 6, and the subsequent closure of line switch 6 in position. f causes another section of the resistor 2 lto be excluded from circuit.

In this way, another uniform decrease of resistance in all three of the phase-winding circuits is accomplished.

It will be noted that, in position 6, the line switch 1 is opened, but this has no effect upon the circuit, since the two outermost sections of the resistor 22 are short-circuited by the switches a and A2 conjointly. Likewise, in position 7'', the line switch 2 and the cam switch A1 are opened, but again no change in the circuits is accomplished thereby, since the other switches that have been closed serve to short-circuit the portions of the accelerating resistors that were originally short-circuited through the use of the switches 2 and Al.

The next progression is begun in this position f by reason of the closure of cam switch A8 which acts conjointly with switch. 1. when the latter is closed in position 9 of the controller to short-circuit a further section of the resistor 22.

In position g,'the line switch 3 and cam switch B1 are opened but no circuit changes are effected thereby, as will be understood from the analogous operation of these switches with respect to those previously described.

Cam switch B3 is also closed in position g and serves, conjointly with line switch 2, which is closed in position it, to short-circuit a third section. of the resistor 23. Line switch l and cam switch C1 are opened in this position without changing the circuit values, while cam switch C3 is actuated to close a gap in a new circuit which is completed in position i of the controller by the closure of line switch In this way, the third section of the resistor 24L is excluded from circuit and another progression has thus been accomplished.

Line switch 5 and cam switch A2 are opened in position 2', while cam switch A4: is closed.

It is believed that no further exposition of the operation of my invention is necessary, since the principlesthat are followed out are considered to be clearly evident from the foregoing description. In general, the line switches, such as switches l and l, that are associated with the resistor 22, are alterternatively employed in conjunction with the successively arranged cam operated switches Al, A2, etc., to exclude from circuit consecutive sections of the resistor, or, in other words, the active tap-point on the resistor is gradually shifted toward the starpoint 25 to which the inner ends of all three resistors are directly connected. Thus, as soon as the line switch i and the cam switch A8 are closed, as indicated in step as, the entire resistor 22 is short-circuited and phase A is thus traversed by current correspond ing to the maximum available speed of the rotor 15.

During the gradual short-circuit of the resistor 22, as just set forth, the other resistors and are also progressively short-circuited, but the corresponding sections of resistance are excluded from circuit in a regular rotation or succession-rather than simultaneously with the exclusion of the corresponding sections of the resistor in this way, a smoothly progressive control. of the rotor phasewinding currents is provided and a desirably steady and uniform acceleration of the induction motor 14 is afforded.

I do not wish to be restricted to the specific circuit connections or arrangement of parts herein set forth, as various modifications thereof may be effected within the spirit and scope of my invention. I desire, therefore, that only such limitations shall be imposed thereon as are indicated in the appended claims.

I claim as my invention:

1. The combination with a plurality of resistors having a common terminal, of means including a plurality of sets of alternately-employed switches for progressively short-circuiting sections of said resistors in a predetermined rotation.

2. The combination with a plurality of resistors having a common terminal, of means including a plurality of sets of alternately-employed switches for progress sively reducing in a predetermined rotation the active values of the resistors measured from said common terminal.

3. The combination with a plurality of resistors having a common terminal, of

means including a plurality of sets ofal- I ternatelyemployed switches for progressively reducing in a predetermined rotation the active values of the resistors measured from said common terminal, each set of said switches having a common terminal con-.

nected to one end of a resistor.

5. The combination with a plurality of resistors having a common terminal, of means including a plurality of sets of alternately-employed switches for progressively short-circuiting sections of said resistors in a predetermined rotation, each set of said switches having a common terminal connected to the outer end of a resistor.

6. The combination with a plurality of resistors having a common terminal, of means including a plurality of sets of alternately-employed switches for progressively reducing in a predetermined rotation the active values of the resistors measured from said common terminal, each set of said switches having a common terminal connected to the outer end of a resistor.

7. The combination with a plurality of resistors having a common terminal, of a plurality of switching devices adapted to be connected to different tap-points of each of said resistors, a plurality of sets of switches adapted to be connected to different groups of said devices, the switches corresponding to any resistor being alternatively closed to efiect a gradual short-circuit of that resistor and the said sets of switches and the devices being closed in a predetermined rotation to eflect progressive control otall resistors.

8. The combination with a plurality of resistors having a common terminal, of a plurality of switching devices adapted to be connected to difierent ta -points of each of said resistors, a plurality of sets of switches adapted to be connected to different groups of said devices, each switch in said sets having one terminal connected to one end of the corresponding resistor, the switches in each of said sets being alternatively closed and the sets together with said devices being progressively closed to effect gradual short-circuit of all resistors.

9. The combination with three star-connected resistors, of a plurality of switching devices adapted to be connected to successive tap-points of each of said resistors, a pair of switches adapted to be connected to alternately-located devices, each pair of switches having a common terminal connected to the outer end of the corresponding resistor, the switches in each pair being alternatively closed and the pairs together with said devices being progressively closed to efl:'ect gradual short-circuit of all resistors.

In testimony whereof, I have hereunto subscribed my name this 30th day of April, 1920.

LLOYD J. HIBBARD. 

